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By H. H

This paper describes the milling practice and operating results of the recently installed heavy-media separation plant of Barton Mines Corporation, the world's largest producer of garnet. This pioneer application of heavy-media separation (sink-float) processes for the beneficiation of a nonmetallic ore is unique in many respects, the details of which will be apparent from the following presentation. Characteristics of the Ore The property is on Gore Mountain, 5 miles west of the village of North Creek, New York, and 11 miles by road. The altitude of the mine is approximately 2800 feet. The valuable mineral, garnet, occurs in a surface deposit, the ore body being about ¾, mile long and varying in width from 50 to 300 ft. The garnet, principally almandite, Fe3Al2 (SiO4)3, occurs in a metamorphic rock of uncertain origin. The gangue mineral is principally hornblende, which constitutes from 40 to 80 per cent of the rock. The remainder of the gangue is divided between plagioclase feldspars and hypersthene, with smaller amounts of biotite, apatite and pyrite. The garnet content of the ore body varies from 5 to 20 per cent of the mass and averages about 10 to I2 per cent. The garnet occurs as crystals, mostly imperfectly developed, known locally as "pockets." These crys- tals vary in size from a fraction of an inch to a foot or more in diameter. Occasionally crystals have been found up to 30 and 36 in. in diameter but they average 4 to 6 inches. Nearly every crystal of garnet is surrounded by a rim of coarsely crystalline hornblende. The quarry faces are striking in appearance, showing crimson-red garnet crystals with their coal black rims scattered over a grayish black background. The specific gravity of the garnet is 3.8 to 4.1 while that of the hornblende ordinarily is 3-07 to 3.24. Some specimens of very dense hornblende have been found with a specific gravity as high as 3.40. The garnet crystals are laminated in structure, and readily cleave into flat, tabular pieces with sharp, chisel-like edges. Even when crushed to a very fine size, the garnet retains this flat, sharp, slivery grain shape. This characteristic, together with its hardness and toughness, gives it its value as an abrasive- Former Operations Mining operations have been carried on for 60 years. Until 1923, only the oxidized (soft rock) section of the ore body was mined. The oxidation, which affected the garnet only slightly, made possible the removal of the garnet from the rock by hand after it was blasted down, using small hand picks. In 1923 a mill was erected on the property, and was rebuilt and redesigned in 1928. Before the adoption of heavy-media separation, concentration was effected by

Jan 1, 1943

By H. H

This paper describes the milling practice and operating results of the recently installed heavy-media separation plant of Barton Mines Corporation, the world's largest producer of garnet. This pioneer application of heavy-media separation (sink-float) processes for the beneficiation of a nonmetallic ore is unique in many respects, the details of which will be apparent from the following presentation. Characteristics of the Ore The property is on Gore Mountain, 5 miles west of the village of North Creek, New York, and 11 miles by road. The altitude of the mine is approximately 2800 feet. The valuable mineral, garnet, occurs in a surface deposit, the ore body being about ¾, mile long and varying in width from 50 to 300 ft. The garnet, principally almandite, Fe3Al2 (SiO4)3, occurs in a metamorphic rock of uncertain origin. The gangue mineral is principally hornblende, which constitutes from 40 to 80 per cent of the rock. The remainder of the gangue is divided between plagioclase feldspars and hypersthene, with smaller amounts of biotite, apatite and pyrite. The garnet content of the ore body varies from 5 to 20 per cent of the mass and averages about 10 to I2 per cent. The garnet occurs as crystals, mostly imperfectly developed, known locally as "pockets." These crys- tals vary in size from a fraction of an inch to a foot or more in diameter. Occasionally crystals have been found up to 30 and 36 in. in diameter but they average 4 to 6 inches. Nearly every crystal of garnet is surrounded by a rim of coarsely crystalline hornblende. The quarry faces are striking in appearance, showing crimson-red garnet crystals with their coal black rims scattered over a grayish black background. The specific gravity of the garnet is 3.8 to 4.1 while that of the hornblende ordinarily is 3-07 to 3.24. Some specimens of very dense hornblende have been found with a specific gravity as high as 3.40. The garnet crystals are laminated in structure, and readily cleave into flat, tabular pieces with sharp, chisel-like edges. Even when crushed to a very fine size, the garnet retains this flat, sharp, slivery grain shape. This characteristic, together with its hardness and toughness, gives it its value as an abrasive- Former Operations Mining operations have been carried on for 60 years. Until 1923, only the oxidized (soft rock) section of the ore body was mined. The oxidation, which affected the garnet only slightly, made possible the removal of the garnet from the rock by hand after it was blasted down, using small hand picks. In 1923 a mill was erected on the property, and was rebuilt and redesigned in 1928. Before the adoption of heavy-media separation, concentration was effected by

Jan 1, 1943

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By Dwight L. Baker, Alexander Knoll

The work herein reported shows that galena in certain organic solutions of fatty acids becomes coated with lead soaps, and that this coating is not only highly water-repellent but is also repellent to certain organic liquids, particularly those of high surface tension; i.e., nitrobenzene, diphenylmethane. Wetting Properties of Galena in Nonaqueous Fatty Acid Solutions When a "captive bubble"I is withdrawn from a polished, plane galena surface under a nitrobenzene solution of stearic acid, the air bubble shows a decided tendency to "cling" to the mineral surface. The contact angle, therefore, was greater than zero, although it was not large enough to be measured quantitatively by the captive-bubble method." When pure nitrobenzene was substituted for the nitrobenzene-stearic acid solution, no clinging of the bubble was observed; viz., contact angle = zero. Although the contact angle developed in air-galena-nitrobenzene-fatty acid solution was small, the organic solvent repellency of the galena surface was great enough to enable good recovery in a laboratory flotation cell2 In Table I are given the results of flotation experiments using several different fatty acids dissolved in nitrobenzene.

Jan 1, 1943

By Alexander Knoll, Dwight L. Baker

The work herein reported shows that galena in certain organic solutions of fatty acids becomes coated with lead soaps, and that this coating is not only highly water-repellent but is also repellent to certain organic liquids, particularly those of high surface tension; i.e., nitrobenzene, diphenylmethane. Wetting Properties of Galena in Nonaqueous Fatty Acid Solutions When a "captive bubble"I is withdrawn from a polished, plane galena surface under a nitrobenzene solution of stearic acid, the air bubble shows a decided tendency to "cling" to the mineral surface. The contact angle, therefore, was greater than zero, although it was not large enough to be measured quantitatively by the captive-bubble method." When pure nitrobenzene was substituted for the nitrobenzene-stearic acid solution, no clinging of the bubble was observed; viz., contact angle = zero. Although the contact angle developed in air-galena-nitrobenzene-fatty acid solution was small, the organic solvent repellency of the galena surface was great enough to enable good recovery in a laboratory flotation cell2 In Table I are given the results of flotation experiments using several different fatty acids dissolved in nitrobenzene.

Jan 1, 1943

By M. D. Hassiallis

The claim is made in a number of patents1'2'3'4 that some compounds of the class known as aryl sulphides have collector properties. One of these patents generalizes the claim to include all aryl sulphides, whose generic formula is R-S2-R' (where x = 1,2, . . . ), with the restriction that if the aromatic radicals R, R' contain substituent groups these groups may not contain nitrogen or oxygen. Moses, Hess, and Perkins cite as evidence for their claims the results of flotation tests on Anaconda and Miami copper ores using diphenyl sulphide, ditolyl disulphide and dinapthyl disul-phide as collectors. The use of alkyl sulphides as collectors has also been reported5 with the conclusion that the alkyl sulphides are better collectors than the corresponding aryl sulphides. The experimental work cited appears to confirm this contention. In order to test these claims with respect to diphenyl sulphide, a sample, purchased from the Eastman Kodak Co., was tested against Anaconda ore. The procedure followed. was that of Moses, Hess, and Perkins. A sample of ore weighing 500 • grams was placed in a laboratory ball mill. To this was added 220 grams of water, 0.06 grams of commercial diphenyl sulphide (1/4 lb. per ton of ore), and 0.8 grams of lime (3 lb. per ton of ore). The material was ground until 93 per cent passed a 65-mesh screen. This pulp was diluted to 16 per cent solids. A sample of the diluted pulp was placed in a Minerals Separation type of laboratory flotation cell. After a a-min. agitation period, pine oil was added and the froth collected for a period of 15 min. This test recovered 68 per cent of the copper, with a ratio of concentration of 6.8:I. The tailing assay was 0.3 per cent Cu. Moses, Hess and Perkins attained a recovery of 75 per cent, with a ratio concentration of I2:I. Although these results do not compare too well with those of Moses, Hess and Perkins, subsequent tests showed an improvement, as judged by vanning of the tails. It is concluded, therefore, that the patent results are confirmed. Contact-angle Tests In order to study the response of the various minerals, found in Anaconda ore, to commercial diphenyl sulphide, some contact-angle tests were made. Polished particles of bornite, chalcodte, chalco-pyrite, pyrite and quartz were conditioned for 15 min. in a suspension of diphenyl sulphide in water. The concentration of this suspension was 0.284 grams per liter, this being the concentration of this reagent in the ball mill. The conditioned particles were rinsed with water (not rubbed with filter paper or boiled linen) and then tested against an air bubble in the bubble machine, with the following results: born-

Jan 1, 1943

By M. D. Hassiallis

The claim is made in a number of patents1'2'3'4 that some compounds of the class known as aryl sulphides have collector properties. One of these patents generalizes the claim to include all aryl sulphides, whose generic formula is R-S2-R' (where x = 1,2, . . . ), with the restriction that if the aromatic radicals R, R' contain substituent groups these groups may not contain nitrogen or oxygen. Moses, Hess, and Perkins cite as evidence for their claims the results of flotation tests on Anaconda and Miami copper ores using diphenyl sulphide, ditolyl disulphide and dinapthyl disul-phide as collectors. The use of alkyl sulphides as collectors has also been reported5 with the conclusion that the alkyl sulphides are better collectors than the corresponding aryl sulphides. The experimental work cited appears to confirm this contention. In order to test these claims with respect to diphenyl sulphide, a sample, purchased from the Eastman Kodak Co., was tested against Anaconda ore. The procedure followed. was that of Moses, Hess, and Perkins. A sample of ore weighing 500 • grams was placed in a laboratory ball mill. To this was added 220 grams of water, 0.06 grams of commercial diphenyl sulphide (1/4 lb. per ton of ore), and 0.8 grams of lime (3 lb. per ton of ore). The material was ground until 93 per cent passed a 65-mesh screen. This pulp was diluted to 16 per cent solids. A sample of the diluted pulp was placed in a Minerals Separation type of laboratory flotation cell. After a a-min. agitation period, pine oil was added and the froth collected for a period of 15 min. This test recovered 68 per cent of the copper, with a ratio of concentration of 6.8:I. The tailing assay was 0.3 per cent Cu. Moses, Hess and Perkins attained a recovery of 75 per cent, with a ratio concentration of I2:I. Although these results do not compare too well with those of Moses, Hess and Perkins, subsequent tests showed an improvement, as judged by vanning of the tails. It is concluded, therefore, that the patent results are confirmed. Contact-angle Tests In order to study the response of the various minerals, found in Anaconda ore, to commercial diphenyl sulphide, some contact-angle tests were made. Polished particles of bornite, chalcodte, chalco-pyrite, pyrite and quartz were conditioned for 15 min. in a suspension of diphenyl sulphide in water. The concentration of this suspension was 0.284 grams per liter, this being the concentration of this reagent in the ball mill. The conditioned particles were rinsed with water (not rubbed with filter paper or boiled linen) and then tested against an air bubble in the bubble machine, with the following results: born-

Jan 1, 1943

By S. F. Ravitz

In his excellent book on the Principles of Flotation, Warkl makes the following significant statement concerning the theory of flotation: Two questions of first-rate importance must be considered . . . First, it must be decided whether the sulfide minerals require a collector in order that they may float, or whether as has been claimed, they possess an inherent float-ability and need no collector. Second, it must be decided whether the xanthate type of collector can react with or be adsorbed by the unchanged sulfide minerals themselves, or whether, as many claim, reaction with the collector is dependent upon initial oxidation of the mineral surface. In the theory of flotation there are no two questions of greater importance than these. Ravitz and Porter2 presented evidence that galena can be floated without a collector, and even without any reagent, provided oxidation products are thoroughly removed from its surface. They found also that thoroughly cleaned galena floated faster when xanthate was used than when a frother alone or no reagent was used, and that, without a collector, the recovery decreased gradually upon exposure of the mineral to air. Their work, however, has met with considerable criticism.l(127).3-6 This paper is presented to answer the objections that have been raised, and to present additional data that confirin their results. The apparatus used to provide oxygen-free conditions for flotation has been described in detail by Ravitz and Porter. An atmosphere of purified nitrogen was maintained within the apparatus; all water and solutions used were freed of dissolved air, and could be transferred where desired by the use of nitrogen Pressure; nitrogen was used as the gaseous medium for flotation. The flotation cell was essentially a glass cylinder 15 cm. long and 4.6 cm. in diameter. Near the bottom was sealed a fritted glass filter, which broke up the gas into small bubbles, and 6 cm. above this filter was a side arm through which the froth overflowed. The pulp was agitated by a glass impeller, which entered the cell through a mercury seal. For each test 17 grams of galena and 75 ml. of water were placed in the cell, after which the speed of the impeller and the rate of gas flow were adjusted. Water was added gradually during the test to keep the froth level at the proper height. The mineral was prepared and cleaned in the following manner. Exceptionally Pure galena was crushed by hand on a clean bucking board, screened to —I50+ 200 mesh, and deslimed on a 200-mesh sieve with a fine spray of water. It was then boiled on a hot plate for a number of hours with several changes of the desired cleaning solution, after which both the solution and the mineral were placed in the "mineral flask" of the apparatus. The cleaning solution was drained off, and the mineral was boiled with oxygen-free water

Jan 1, 1943

By S. F. Ravitz

In his excellent book on the Principles of Flotation, Warkl makes the following significant statement concerning the theory of flotation: Two questions of first-rate importance must be considered . . . First, it must be decided whether the sulfide minerals require a collector in order that they may float, or whether as has been claimed, they possess an inherent float-ability and need no collector. Second, it must be decided whether the xanthate type of collector can react with or be adsorbed by the unchanged sulfide minerals themselves, or whether, as many claim, reaction with the collector is dependent upon initial oxidation of the mineral surface. In the theory of flotation there are no two questions of greater importance than these. Ravitz and Porter2 presented evidence that galena can be floated without a collector, and even without any reagent, provided oxidation products are thoroughly removed from its surface. They found also that thoroughly cleaned galena floated faster when xanthate was used than when a frother alone or no reagent was used, and that, without a collector, the recovery decreased gradually upon exposure of the mineral to air. Their work, however, has met with considerable criticism.l(127).3-6 This paper is presented to answer the objections that have been raised, and to present additional data that confirin their results. The apparatus used to provide oxygen-free conditions for flotation has been described in detail by Ravitz and Porter. An atmosphere of purified nitrogen was maintained within the apparatus; all water and solutions used were freed of dissolved air, and could be transferred where desired by the use of nitrogen Pressure; nitrogen was used as the gaseous medium for flotation. The flotation cell was essentially a glass cylinder 15 cm. long and 4.6 cm. in diameter. Near the bottom was sealed a fritted glass filter, which broke up the gas into small bubbles, and 6 cm. above this filter was a side arm through which the froth overflowed. The pulp was agitated by a glass impeller, which entered the cell through a mercury seal. For each test 17 grams of galena and 75 ml. of water were placed in the cell, after which the speed of the impeller and the rate of gas flow were adjusted. Water was added gradually during the test to keep the froth level at the proper height. The mineral was prepared and cleaned in the following manner. Exceptionally Pure galena was crushed by hand on a clean bucking board, screened to —I50+ 200 mesh, and deslimed on a 200-mesh sieve with a fine spray of water. It was then boiled on a hot plate for a number of hours with several changes of the desired cleaning solution, after which both the solution and the mineral were placed in the "mineral flask" of the apparatus. The cleaning solution was drained off, and the mineral was boiled with oxygen-free water

Jan 1, 1943

By Keith Leonard Sutherland

This paper is a study of the differential flotation of the sulphide minerals in the presence of salts of silver, lead and zinc. In practice, accidental activation due to these salts is more important than their use as reagents to replace copper sulphate. The general method of investigation has been based upon contact tests, the temperature of 35°C being chosen in conformity with earlier work. Potassium ethyl xanthate and potassium amyl xanthate were selected as collectors and pure sulphide minerals were used. The experimental procedure has been outlined in earlier papers and all solutions were kept carbonate-free.14 Contact, or spreading of an air bubble, at a mineral surface indicates the presence of an adsorbed collector film. Purity of Reagents The xanthates were purified in the usual manner.' Neither the cyanide nor the sodium hydroxide solutions contained sufficient carbonate to give a precipitate with barium chloride solution. The silver sulphate was prepared from pure silver nitrate by evaporation with concentrated sulphuric acid until there was no evidence of brown fumes, This solution was diluted and the difficultly soluble sulphate washed with water so that unchanged nitrate was dissolved. The resultant crystalline powder was pure white. The lead and zinc salts were prepared by dissolving especially pure lead and zinc in C.P. nitric and sulphuric acid solution and the crystals drained. The standard solutions were checked by titration. It was felt desirable to use the sulphate radical wherever possible, but since lead sulphate was insufficiently soluble for the purpose of the experiments, it was necessary to use some other lead salt. A.R. copper sulphate was used without further purification. Results The results are presented in the accompanying figures; the areas of noncontact (nonflotation) are shaded in Figs. 8, 9, 10 and 11; in the remainder they lie to the right of the curve. Zinc Sulphate The curves in Fig. I are to be compared with those for Fig. 2, for which zinc sulphate is absent. This comparison shows that the influence of the zinc ion is usually small. Its influence is more marked, however, for chalcopyrite in the absence of cyanide. The influence of zinc sulphate is also marked for copper-activated sphalerite, for which tests were made only in the "absence of cyanide. The results are of importance in the separation of pyrite from copper-activated sphalerite when zinc sulphate is added in the lead flotation section (p. 204 of ref. I). Sphalerite does not adsorb the collector (i.e., become floatable) under the conditions chosen.

Jan 1, 1943

By Keith Leonard Sutherland

This paper is a study of the differential flotation of the sulphide minerals in the presence of salts of silver, lead and zinc. In practice, accidental activation due to these salts is more important than their use as reagents to replace copper sulphate. The general method of investigation has been based upon contact tests, the temperature of 35°C being chosen in conformity with earlier work. Potassium ethyl xanthate and potassium amyl xanthate were selected as collectors and pure sulphide minerals were used. The experimental procedure has been outlined in earlier papers and all solutions were kept carbonate-free.14 Contact, or spreading of an air bubble, at a mineral surface indicates the presence of an adsorbed collector film. Purity of Reagents The xanthates were purified in the usual manner.' Neither the cyanide nor the sodium hydroxide solutions contained sufficient carbonate to give a precipitate with barium chloride solution. The silver sulphate was prepared from pure silver nitrate by evaporation with concentrated sulphuric acid until there was no evidence of brown fumes, This solution was diluted and the difficultly soluble sulphate washed with water so that unchanged nitrate was dissolved. The resultant crystalline powder was pure white. The lead and zinc salts were prepared by dissolving especially pure lead and zinc in C.P. nitric and sulphuric acid solution and the crystals drained. The standard solutions were checked by titration. It was felt desirable to use the sulphate radical wherever possible, but since lead sulphate was insufficiently soluble for the purpose of the experiments, it was necessary to use some other lead salt. A.R. copper sulphate was used without further purification. Results The results are presented in the accompanying figures; the areas of noncontact (nonflotation) are shaded in Figs. 8, 9, 10 and 11; in the remainder they lie to the right of the curve. Zinc Sulphate The curves in Fig. I are to be compared with those for Fig. 2, for which zinc sulphate is absent. This comparison shows that the influence of the zinc ion is usually small. Its influence is more marked, however, for chalcopyrite in the absence of cyanide. The influence of zinc sulphate is also marked for copper-activated sphalerite, for which tests were made only in the "absence of cyanide. The results are of importance in the separation of pyrite from copper-activated sphalerite when zinc sulphate is added in the lead flotation section (p. 204 of ref. I). Sphalerite does not adsorb the collector (i.e., become floatable) under the conditions chosen.

Jan 1, 1943

By G. B. Walker, S. A. Falconer, S. J. Swainson, H. H. Vogel

During the past few years much interest and attention has been focused on a relatively new method of ore concentration, which utilizes the principles of sink and float and employs as the heavy medium a suspension in water of a finely ground solid, such as galena or ferrosilicon. Although a relatively recent development, much progress has already been made in applying heavy-media separation processes to a considerable number of ores. Eight plants in this country and abroad are now treating approximately 10 million tons of ore annually by heavy-media separation (sink-float) processes, including lead-zinc, lead, iron, garnet, tin and tungsten. At the annual meeting of the A.I.M.E. in 1941, three interesting papers (unpublished) dealing with heavy-media separation (sink-float) processes of ore concentration as practiced in four commercial units in the United States were presented by Victor Rakowsky, Grover Holt, Elmer Isern and Robert Ammon. These papers gave an excellent exposition of the principles of sink and float, as well as the operating practice in two iron-ore-beneficiation plants, the Harrison and the Merritt, of Butler Brothers, in Minnesota; the Central mill of the Eagle Picher Mining and Smelting Co.; and the Mascot mill, of the American Zinc, Lead and Smelting Co. Augmented by pictorial descriptions and a working model demonstrating the processes, these papers evoked a great deal of interest and discussion. In fact, in reporting the high lights of the meeting in the April 1941 issue of Mining and Metallurgy, Professor Taggart made the statement that " preconcentration by heavy suspension was Miss A.1.M.E 1941 so far as milling is concerned." Although to date the greatest application of heavy-media separation from the tonnage point of view has been for the treatment of lead, zinc and iron ores, these processes have a much wider field of usefulness. In this regard, it is to be noted that recently new heavy-media separation plants for treating cassiterite ore and garnet ore have been placed in successful operation. Moreover, numerous other types of ores have been found to respond well to these processes when tested on a semi-commercial scale, and it is expected that in the near future a considerable number of new plants will be erected. In view of the fact that heavy-media separation processes offer such attractive possibilities, particularly now, when the mining industry is being called on for an even larger production than ever before has been attempted, despite shortages of labor and supplies, it was felt that a description of some of the successful separations that have been worked out during the past year in the Ore Dressing Laboratory of the American Cyanamid Co. on a variety of ores of strategic importance would be of interest. The purpose of this paper, therefore, is to present the essential data relating to investigations of heavy-

Jan 1, 1943

By G. B. Walker, S. J. Swainson, S. A. Falconer, H. H. Vogel

During the past few years much interest and attention has been focused on a relatively new method of ore concentration, which utilizes the principles of sink and float and employs as the heavy medium a suspension in water of a finely ground solid, such as galena or ferrosilicon. Although a relatively recent development, much progress has already been made in applying heavy-media separation processes to a considerable number of ores. Eight plants in this country and abroad are now treating approximately 10 million tons of ore annually by heavy-media separation (sink-float) processes, including lead-zinc, lead, iron, garnet, tin and tungsten. At the annual meeting of the A.I.M.E. in 1941, three interesting papers (unpublished) dealing with heavy-media separation (sink-float) processes of ore concentration as practiced in four commercial units in the United States were presented by Victor Rakowsky, Grover Holt, Elmer Isern and Robert Ammon. These papers gave an excellent exposition of the principles of sink and float, as well as the operating practice in two iron-ore-beneficiation plants, the Harrison and the Merritt, of Butler Brothers, in Minnesota; the Central mill of the Eagle Picher Mining and Smelting Co.; and the Mascot mill, of the American Zinc, Lead and Smelting Co. Augmented by pictorial descriptions and a working model demonstrating the processes, these papers evoked a great deal of interest and discussion. In fact, in reporting the high lights of the meeting in the April 1941 issue of Mining and Metallurgy, Professor Taggart made the statement that " preconcentration by heavy suspension was Miss A.1.M.E 1941 so far as milling is concerned." Although to date the greatest application of heavy-media separation from the tonnage point of view has been for the treatment of lead, zinc and iron ores, these processes have a much wider field of usefulness. In this regard, it is to be noted that recently new heavy-media separation plants for treating cassiterite ore and garnet ore have been placed in successful operation. Moreover, numerous other types of ores have been found to respond well to these processes when tested on a semi-commercial scale, and it is expected that in the near future a considerable number of new plants will be erected. In view of the fact that heavy-media separation processes offer such attractive possibilities, particularly now, when the mining industry is being called on for an even larger production than ever before has been attempted, despite shortages of labor and supplies, it was felt that a description of some of the successful separations that have been worked out during the past year in the Ore Dressing Laboratory of the American Cyanamid Co. on a variety of ores of strategic importance would be of interest. The purpose of this paper, therefore, is to present the essential data relating to investigations of heavy-

Jan 1, 1943

By James Norman, O. C. Ralston, John Dasher

Most mineral products are used in the finely divided state, but some are sold in larger sizes. Coal, gravel, metallurgical fluorspar, phosphate rock, hematite, chro-mite, and other products are sold in sizes coarser than can be treated by many mineral-dressing methods. Gravity separation of coarser sizes by log washing and jigging is probably as ancient as any process now in use. The performance of jigs on a feed with sufficient difference in density of the minerals is excellent, but many families of minerals are too similar in density to be separated effectively by this method. The use of heavy suspensions of fine solids to separate coarse coal from bone and slate has been in use for some years. This separation by sink-and-float was limited until recently to light minerals. Development of galena and ferrosilicon as suspension media, by Minerals Beneficia-tion, Inc., at Mascot, Tenn., Pitcher, Okla., and Crosby, Minn., under patents granted during and since 1938, has permitted excellent results to be obtained on minerals of very similar densities up to 3.3. This process has been put In the hands of American Cyanamid Co. for exploitation, and further research now in progress may increase the density of suspension obtainable so that separations at a density of 4.0 may be practicable before this is published. The Huntington-Heberlein dense-medium process, developed in England, is also being commercialized in the United States by Sink and Float Corporation. Du Pont has developed a sink-and-float separation using halogenated hydrocarbons as parting liquids; at this writing, the method is used commercially only on coal but has been successful in the pilot plant on many other minerals using tetrabrom-ethane at densities up to 2.95. While these processes were being developed to extend the range of separation by difference in density to the coarser sizes, the Bureau of Mines was engaged in developing a process that will extend the range of separation by difference in wettability up to 2-in. size. War work has pushed aside its further development indefinitely. The results are published here with the hope that some use may be suggested that will justify post-war development, and so that readers that may be able to make immediate use of the scheme may have the information. Earlier Work It has been known since the time of Herodotus (B.C. 484(?)-425) that water-repellent particles will adhere to sticky surfaces. That early historian reports the recovery of gold from the mud of a lake

Jan 1, 1943

By James Norman, O. C. Ralston, John Dasher

Most mineral products are used in the finely divided state, but some are sold in larger sizes. Coal, gravel, metallurgical fluorspar, phosphate rock, hematite, chro-mite, and other products are sold in sizes coarser than can be treated by many mineral-dressing methods. Gravity separation of coarser sizes by log washing and jigging is probably as ancient as any process now in use. The performance of jigs on a feed with sufficient difference in density of the minerals is excellent, but many families of minerals are too similar in density to be separated effectively by this method. The use of heavy suspensions of fine solids to separate coarse coal from bone and slate has been in use for some years. This separation by sink-and-float was limited until recently to light minerals. Development of galena and ferrosilicon as suspension media, by Minerals Beneficia-tion, Inc., at Mascot, Tenn., Pitcher, Okla., and Crosby, Minn., under patents granted during and since 1938, has permitted excellent results to be obtained on minerals of very similar densities up to 3.3. This process has been put In the hands of American Cyanamid Co. for exploitation, and further research now in progress may increase the density of suspension obtainable so that separations at a density of 4.0 may be practicable before this is published. The Huntington-Heberlein dense-medium process, developed in England, is also being commercialized in the United States by Sink and Float Corporation. Du Pont has developed a sink-and-float separation using halogenated hydrocarbons as parting liquids; at this writing, the method is used commercially only on coal but has been successful in the pilot plant on many other minerals using tetrabrom-ethane at densities up to 2.95. While these processes were being developed to extend the range of separation by difference in density to the coarser sizes, the Bureau of Mines was engaged in developing a process that will extend the range of separation by difference in wettability up to 2-in. size. War work has pushed aside its further development indefinitely. The results are published here with the hope that some use may be suggested that will justify post-war development, and so that readers that may be able to make immediate use of the scheme may have the information. Earlier Work It has been known since the time of Herodotus (B.C. 484(?)-425) that water-repellent particles will adhere to sticky surfaces. That early historian reports the recovery of gold from the mud of a lake

Jan 1, 1943

By Foster Fraas

Most commercial electrostatic separators utilize the electrical property of conductivity, but although based on the same principles, they are constructed in a variety of forms, a common one being the simple roll type. Some information obtained during an investigation of that type of separator, and which indirectly is applicable to other types, is presented here. In Fig. I material discharged from hopper 6 is fed onto grounded rotating roll 2. Electrode 3 is at a high electrical potential with respect to roll 2, and any conductive particle in contact with roll 2 therefore acquires an electrical charge of such polarity that, when present in the electrical field, the force on it is in the direction of electrode 3. A detailed description of the charging by conductance as utilized in electrostatic separators may be found in a previous publication.' As a result of this force, the path of the projected particle is changed in increasing amounts in the direction toward region C as the magnitude of the charge is increased. With the dividing edge 4 the projected particles may be divided into two fractions —those in region C designated as "deflected" or"deflectant"and those in region B designated as "residue." When material is passed over the roll only once, a complete separation is seldom obtained, therefore most commercial separators contain several roll-separator units in series, and some practical machines use as many as I2. In this paper a "pass" means the passage of material over a single-roll unit. The procedure is to repass either residue B with a low potential on electrode 3 or deflectant C with a high potential on 3. Most electrostatic separations follow a flowsheet of roughing and cleaning either the concentrate or the tailing, or both. In a specific instance, a dry, heated mixture of wet cleaned chromite and garnet from an

Jan 1, 1943

By Foster Fraas

Most commercial electrostatic separators utilize the electrical property of conductivity, but although based on the same principles, they are constructed in a variety of forms, a common one being the simple roll type. Some information obtained during an investigation of that type of separator, and which indirectly is applicable to other types, is presented here. In Fig. I material discharged from hopper 6 is fed onto grounded rotating roll 2. Electrode 3 is at a high electrical potential with respect to roll 2, and any conductive particle in contact with roll 2 therefore acquires an electrical charge of such polarity that, when present in the electrical field, the force on it is in the direction of electrode 3. A detailed description of the charging by conductance as utilized in electrostatic separators may be found in a previous publication.' As a result of this force, the path of the projected particle is changed in increasing amounts in the direction toward region C as the magnitude of the charge is increased. With the dividing edge 4 the projected particles may be divided into two fractions —those in region C designated as "deflected" or"deflectant"and those in region B designated as "residue." When material is passed over the roll only once, a complete separation is seldom obtained, therefore most commercial separators contain several roll-separator units in series, and some practical machines use as many as I2. In this paper a "pass" means the passage of material over a single-roll unit. The procedure is to repass either residue B with a low potential on electrode 3 or deflectant C with a high potential on 3. Most electrostatic separations follow a flowsheet of roughing and cleaning either the concentrate or the tailing, or both. In a specific instance, a dry, heated mixture of wet cleaned chromite and garnet from an

Jan 1, 1943

By Alfonso Rizo-Patrón, A.M. Gaudin

Previous studies of activation in flotation have directed attention to the action of the activator on the mineral to be floated rather than to the relationship of the activator to the collector. The latter phase of the problem, however, seems to have definite scientific, if not also practical, interest. In the investigation reported in this paper, experiments were carried out, largely with quartz as subject, barium as activator, and oleate as collector. The results obtained indicate that a I: I ratio of collector ion to activator ion gives optimum results, and that a 2:1 ratio almost fails to achieve activation and flotation. Yet, a 2:I ratio would have been expected on stoichiometric grounds, had the coating been a normal salt of the activator ion with the collector ion, since barium is a divalent cation and oleate a monovalent anion. To interpret and rationalize the observations, considerations of the crystal chemistry of quartz are helpful. The point of view to which these considerations lead may be of general applicability to systems involving suspensions of solids in liquids; they confirm that an adsorbed coating is inescapable. Apparatus and Supplies The experimental work consisted in barium-ion abstraction tests, hydrogen-ion and hydroxyl-ion abstraction tests, flotation tests, and determinations of the surface of the crushed quartz. The flotation machine was built according to the design of D. W. McGlashan.* It consists of a drill press in which the bit has been replaced by a stainless-steel impellor surrounding a stainless-steel sta-tor, as in the Fagergren laboratory machine. The air intake is controlled by a valve, and the cell consists of a beaker. The quartz was obtained from vein quartz stored in large chunks. It was first crushed to 20 mesh, then sized on a 28-mesh screen. The 20 to 28-mesh size alone was retained for use. This size was freed of coarse iron by passage through a Ball-Norton magnetic separator, bleached with boiling hydrochloric acid to remove residual abraded iron, washed with distilled water until the washings were thoroughly free of ferrous, ferric, and excess hydrogen ion, and stored in covered Pyrex beakers under water until used. The barium was used as barium chloride, Baker's analyzed C. P. The oleate was used as sodium oleate. It was prepared from sodium hydroxide, Baker's analyzed C. P., and oleic acid purified by R. R. de Arellano3 in the laboratories at the Massachusetts Institute of Technology. The purification procedure was elaborated from the recent $researches of Brown and Shinowara.2 It consisted in: (I) saponification of olive oil with potassium

Jan 1, 1943

By Alfonso Rizo-Patrón, A. M. Gaudin

Previous studies of activation in flotation have directed attention to the action of the activator on the mineral to be floated rather than to the relationship of the activator to the collector. The latter phase of the problem, however, seems to have definite scientific, if not also practical, interest. In the investigation reported in this paper, experiments were carried out, largely with quartz as subject, barium as activator, and oleate as collector. The results obtained indicate that a I: I ratio of collector ion to activator ion gives optimum results, and that a 2:1 ratio almost fails to achieve activation and flotation. Yet, a 2:I ratio would have been expected on stoichiometric grounds, had the coating been a normal salt of the activator ion with the collector ion, since barium is a divalent cation and oleate a monovalent anion. To interpret and rationalize the observations, considerations of the crystal chemistry of quartz are helpful. The point of view to which these considerations lead may be of general applicability to systems involving suspensions of solids in liquids; they confirm that an adsorbed coating is inescapable. Apparatus and Supplies The experimental work consisted in barium-ion abstraction tests, hydrogen-ion and hydroxyl-ion abstraction tests, flotation tests, and determinations of the surface of the crushed quartz. The flotation machine was built according to the design of D. W. McGlashan.* It consists of a drill press in which the bit has been replaced by a stainless-steel impellor surrounding a stainless-steel sta-tor, as in the Fagergren laboratory machine. The air intake is controlled by a valve, and the cell consists of a beaker. The quartz was obtained from vein quartz stored in large chunks. It was first crushed to 20 mesh, then sized on a 28-mesh screen. The 20 to 28-mesh size alone was retained for use. This size was freed of coarse iron by passage through a Ball-Norton magnetic separator, bleached with boiling hydrochloric acid to remove residual abraded iron, washed with distilled water until the washings were thoroughly free of ferrous, ferric, and excess hydrogen ion, and stored in covered Pyrex beakers under water until used. The barium was used as barium chloride, Baker's analyzed C. P. The oleate was used as sodium oleate. It was prepared from sodium hydroxide, Baker's analyzed C. P., and oleic acid purified by R. R. de Arellano3 in the laboratories at the Massachusetts Institute of Technology. The purification procedure was elaborated from the recent $researches of Brown and Shinowara.2 It consisted in: (I) saponification of olive oil with potassium

Jan 1, 1943